1. Field of the Invention
The present invention is related to a method of data transmission in a wireless network system having a multi-layer structure, and more particularly, to a method of increasing data throughput of a wireless network system by dynamically adjusting MTU/fragmentation size according to current transmission status.
2. Description of the Prior Art
With rapid development in technology, a user may easily connect to a network using desktop computers, notebook computers, personal digital assistants (PDAs) or smart phones. In order for electronic equipment having varying specifications to be able to communicate with other entities in the same network, an OSI (Open Systems Interconnection) network model has been provided by ISO (International Organization for Standardization) for managing the network intercommunication between two network entities.
Third generation (3G) and fourth generation (4G) wireless networks, as specified by the 3rd Generation Partnership Project (3GPP) include wireless access networks in which different application services, such as data services, voice over IP (VoIP) content or video content, can be delivered over various communication protocols, such as Internet protocol (IP) and Transmission Control Protocol (TCP). Both IP and TCP define size limits for packets transmitted over a network. The IP maximum transmission unit (MTU) defines the maximum size of IP packet that can be transmitted. The TCP maximum segment size (MSS) defines the maximum number of data bytes in a packet (excluding the TCP/IP headers).
In computer networking, the size of an MTU/fragmentation may be fixed according to the adopted network access interfaces (such as Ethernet, WLAN, Token Ring or FDDI) or determined by relevant systems (such as point-to-point serial links) at connecting time. A larger MTU/fragmentation size brings greater efficiency improves bulk protocol throughput because each packet carries more user data while protocol overheads remain fixed. A larger MTU/fragmentation size also means processing of fewer packets for the same amount of data, especially in a system where per-packet-processing is a critical performance limitation. However, large packets occupy a slow link for more time than a smaller packet, causing greater delays to subsequent packets, and increasing lag and minimum latency. Large packets are also problematic in the presence of communications errors since larger packets are more likely to be corrupt at a given bit error rate. Corruption of a single bit in a packet requires that the entire packet be retransmitted, and retransmissions of larger packets take longer due to greater payload.
Therefore, there is a need for a method of dynamically adjusting MTU/fragmentation size to optimize data throughput rate.